單選題Enginesaretomachines_______heartsa

C解析此題主要測(cè)試以下句型結(jié)構(gòu)：A is to B what C is to D。意思：A對(duì)于B的重要性，就如同C對(duì)于D的重要性一樣。此句型中what從句在主句中起表語作用，同時(shí)what在從句中也起表語作用（這一點(diǎn)老師應(yīng)該掌握，然而學(xué)生只需記住該句型結(jié)構(gòu)即可）。例如：Railway is to transportation what blood is to a man's body。鐵路對(duì)于交通的重要性，就如同血液對(duì)于身體的重要性一樣。